Crossed-field discharge device and coupler therefor and microwave circuits incorporating the same



July l5, 1969 J. E. sTAATs 3,456,151

cRossED-FIELD DISCHARGE Dvc AND COUPLER THEREFOR 1 AND MICROWAVE CIRCUITS lNCoRPoRATING THE SAME Filed July 27, 1966 7 Sheets-Sheet 1 ATTYS.

July 15, 1969 J. E. sTAATs 3,456,151

CROSSED-F1ELD DISCHARGE DEVICE AND COUILLIR THEREF'OR AND MICROWAVE CIRCUITS INCORPORATING THE SAME Filed July 27, 1966 '7 Sheets-Sheet 2 H Y 224 I 4 `l 716.2 2 7 239 242 24/1 240 July 15, 1969 J. E. sTAATs 3,456,151

CROSSED-FIELD DISCHARGE DEVTCE AND COULER THEREFOR AND MICROWAVE CIRCUITS INCORPORA'IING THE SAME Filed July 27, 1966 7 Sheets-Sheet :5

July 15, 1969 J. E. STAATS 3,456,151

CROSSED-F1ELD DISCHARGE DEVCE ANI) (JO'JILER IIEREFOR AND MICROWAVE CIRCUITS TNCORPORA'I'ING THE SAME Filed July 27, 1966 '7 Sheets-Sheet 4 J. E. STAATS July 15, 1969 3,456,151 CROssEuFu-LD mscHARG DEVICE ANI) coul'msn THEREPOR AND MICROWAVE CIRCUITS [NCORPORA'IING THE SAME Filed July 27, 1966 7 Sheets-Sheet b July l5, 1969 J. E. STAATS 3,456,151

CHOSSED-FIELD DISCHARGE DEVTCE ANI) (,OUI'LIIR 'IHEREFOR AND MCROWAVE CIRCUITS INCORPORA'IING THM SAMIII Filed July 27, 1966 '7 Sheets5heet 'f FGJZ United States Patent U.S. Cl. 315-3951 34 Claims ABSTRACT OF THE DISCLOSURE There is disclosed a crossed-field discharge device including an annular sleeve surrounding a pair of segmented and axially spaced-apart annular anode members and defining therewith a first annular space, the anode segments defining axially extending recesses therebetween, and each anode segment including an axially extending rod integral therewith, rods on each anode member respectively disposed in the recesses of the other anode member, and an axially extending cathode structure having a plurality of electron emissive sections thereon surrounded by the anode members, all input and output leads for the device being connected at one end thereof; embodiments respectively having one and two magnetic field coils are disclosed.

The present invention relates to an improved crossedeld discharge device, and an improved coupler therefor, and microwave circuits incorporating the same including a microwave oscillator circuit.

It is a general object of the invention to provide a new and improved crossed-field discharge device for use at microwave frequencies, which device is of exceedingly simple and economical construction and arrangement, and which device is particularly adapted for operation upon the application of relatively low voltage operating potentials thereto.

Another object of the invention is to provide an improved crossed-iield discharge device of the type set forth which can provide a high output of microwave energy in proportion to the physical dimensions thereof, whereby to permit the miniaturization of microwave circuits embodying the improved crossed-field discharge device of the present invention.

Still another object of the invention is to provide a crossed-field discharge device of the type set forth including an anode structure defining an axially extending space therethrough,a pair of pole pieces respectively arranged adjacent to the opposite ends of the anode structure, a plurality of axially extending anode segments on the anode structure and projecting radially into the axially extending space and providing a corresponding plurality of axially extending anode recesses therebetween, a plurality of rods respectively disposed in the anode recesses and respectively spaced from the adjacent ones of the anode segments, means electrically interconnecting therods at the corresponding ends thereof, an axially extending annular emissive cathode disposed in the axially extending space and cooperating with the anode structure to define an axially extending annular interaction space, a heater for the cathode disposed therein, a first connector commonly electrically connected both to the cathode and to one terminal of the heater and extending outwardly from the device through one end of the anode structure, a second connector connected to the other terminal of the heater and extending outwardly from the device through the one end of the anode structure, means enclosing and sealing the other end of the anode structure and the associated end of the axially extending space, and an end structure enclosing and sealing the one end of "ice the anode structure and the associated end of the axially extending space and receiving the connectors therethrough for mechanically supporting the cathode and the heater with respect to the anode structure while providing electrical insulation among the anode structure and the connectors.

I connection with the foregoing object it is another object of the invention to provide improved crossed-field discharge devices of the type set forth, wherein the end structure is the only electrically insulating seal for the device, and the cathode and the one terminal of the heater are interconnected at the ends thereof disposed away from the one end of the anode structure.

Another object of the invention is to provide an improved crossed-field discharge device of the type set forth wherein the cathode includes an annular wall of electrically conductive material and completely enclosing the heater and extending to the exterior of the device through the one end of the anode structure, thereby to prevent the introduction of FR energy into the heater and the second connector.

Another object of the invention is to provide an improved crossed-eld discharge device of the type set forth wherein the first connector is a annular conductor disposed about and receiving therethrough the second connector.

It is another object of the invention to provide an improved crossed-eld discharge device of the type set forth incorporating therein an improved anode structure of a folded cavity interdigital type providing a resonant cavity for the operation of the device in a microwave oscillator circuit.

Yet another object of the invention is to provide an improved microwave oscillator incorporating therein a crossed-field discharge device of the present invention.

A further object of the invention is to provide an improved microwave coupling structure for connection to the input and output terminals of the crossed-field discharge device of the present invention.

A still further object of the invention is to provide a microwave assembly including the crossed-field discharge device of the present invention in combination with the microwave coupling structure of the present invention.

A still further object of the invention is to provide a microwave assembly including the crossed-field discharge device of the present invention in combination with a field coil disposed therearound and with the axis `of the magnetic field produced thereby disposed at the longitudinal axis of the associated device, one preferred form of the invention including two field coil sections disposed longitudinally beyond the ends of the anode structure of the device, and another preferred form of the invention `providing a single field coil section with the longitudinal midplane thereof disposed at the longitudinal midpoint of the anode structure of the device, the microwave assembly in the latter case also preferably including a sleeve of heat conductive material extending longitudinally beyond the outer ends of the anode structure and carrying on the portions thereof disposed beyond the ends of the field coil section a plurality of cooling fins.

Further features of the invention pertain to the particular arrangement of the 4parts of the crossed-field discharge device of the coupler therefor and the connection thereof in various microwave circuits, whereby the aboveoutlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification when taken in connection with the accompanying drawings, in which:

FIGURE l is a schematic and diagrammatical illustration of an oscillator circuit incorporating therein a crossedfield discharge device of the present invention;

FIG. 2 is a view in vertical section through the oscillator of FIG. 1 and illustrating the circuit connections for the crossed-field discharge device including the magnetic field coils therefor and the coupler and filter co-nstruction used therewith;

FIG. 3 is an enlarged view in vertical section through the crossed-field discharge device illustrated in the oscillator of FIG. 2;

FIG. 4 is a partial horizontal section through the device of FIG. 3 along the line 4 4 thereof;

FIG. 5 is an enlarged view in horizontal section through the device of FIG. 3 along the line 5 5 thereof;

FIG. 6 is a partial view in horizontal section through the device of FIG. 3 along line 6 6 thereof;

FIG. 7` is a fragmentary perspective view of portions of the two anode members forming a part of the device of FIGS. 2 to 6, the anode members being illustrated in a spaced apart position;

FIG. 8 is an end View of one of the anode members forming a part of the crossed-eld discharge device of FIGS. 3 to 6;

FIG. 9 is a View in vertical section through the anode member of FIG. 8 along the line 9 9 thereof;

FIG. 10 is a partial diagrammatical lineal view as seen within the anode members of FIGS. 7 to 9;

FIG. 11 is a view in vertical section through another form of the oscillator of FIG. 1 and illustrating the circuit connections for the crossed-field discharge device when a single magnetic field coil and return structure therefor are utilized about the longitudinal mid-portion of the crossed-field discharge device; and

FIG. 12 is an enlarged view in vertical section through the crossed-field discharge device illustrated in the o-scillator 0f FIG. ll and including a portion of the field winding and magnetic return path therefor.

Referring to FIG. 1 of the drawings, there is diagrammatically illustrated an oscillator circuit 50 embodying the features of the present invention, the oscillator circuit '50 having been illustrated as connected to a three-wire Edison network of 236 volts, single-phase 60-cycles AC, and including two ungrounded line conductors L1 and L2 and a grounded neutral conductor N, the three conductors mentioned being terminated at an associated electrical insulating block B. The circuit 50 also comprises a power supply 51 having a pair of input terminals 52 and 53 that are respectively connected to the conductors L1 and L2. A first pair of output terminals 54 and 55 is provided for supplying a rectified and filtered DC voltage of low amplitude for the purpose of applying the DC operating potential to the crossed-field discharge device of the oscillator circuit 50; and a second pair of output lterminals 56 and 57 is provided for supplying a relatively low voltage AC power for the purpose of energizing the heater of the crossed-field discharge device of the oscillator circuit 50. More specifically, the input terminals 52 and '53 are connected to the output terminals 54 and 55 by a converter, the converter preferably being of the type disclosed in the copending application of James E. Staats, Ser. No. 181,144, filed Mar. 20, 1962, wherein there is disclosed a converter comprising an assembly of capacitors and rectifiers connected between the inp-ut terminals and the output terminals thereof, and characterized by the production of a DC output voltage across the output terminals thereof in response to the application of a low frequency AC input thereto across the input terminals thereof, whereby the amplitude of the DC output voltage from the converter is approximately twice the peak value of the AC voltage to the converter. The converter described is in fact a voltage doubler and rectifier circuit wherein the output DC potential therefrom at the terminals 54 and 55 is approximately 666 volts when the AC supply source has an R.M.S. voltage of 2.36 volts between the conductors L1 and L2, the 666 volts DC being the open circuitl or no-load value for the DC output from the power supply 51.

The oscillator circuit further comprises an oscillator 200 incorporating therein a crossed-field discharge device 100 made in accordance with and embodying the principles of the present invention, the oscillator 200 having a pair of input terminals 201 and 202 that are connected respectively to the DC output terminals 54 and 55 of the power supply 51 by means of conductors 60 and 61, respectively; the input terminal 202 is also connected by the conductor 61 to one of the low voltage AC output terminals 56 of the power supply 51. A third input terminal 203 is provided for the oscillator 200, the input terminal 203 being connected by a conductor 62 to the other low voltage AC output terminal 57 of the power supply 51. As illustrated, all of the parts of the oscillator 200 are surrounded by a metallic casing 205 to which is connected as at 206 to an outer tubular conductor 207 within which is disposed an inner tubular conductor 190 that is also connected to the input terminal 202, the coaxial conductors 190 and 207 providing an output connection for the oscillator 200. Connection is made to an output transmission line 65 including an outer tubular conductor 66 and an inner conductor 67 disposed therein, a first capacitive coupling being provided by a coupler 242 between the outer conductor 207 and the outer conductor 66, and a second capacitive coupling being provided by the coupler 247 between the inner conductor 190 and the inner conductor 67. The capacitive coupling provided by the couplers 242 and 247 is desirable and necessary since for safety purposes the outer conductor 66 of the transmission line 65 must be grounded, which grounding of the outer conductor 66 is not possible if there is a DC connection to the oscillator casing 205, the casing 205 having a potential with respect to ground because of the application of operating potentials thereto from the voltage doubler and rectifier circuit 51, it being inherent in the construction and operation of the circuit 51 that neither the conductor 60 nor the conductor 61 can be grounded. Accordingly, it is also necessary and desirable that the power supply 51 and the oscillator 200 be electrically shielded by a grounded outer housing (not shown) disposed therearound, all as is fully described in the aforementioned copending application Ser. No. 181,144.

The microwave energy supplied from the oscillator 200 to the transmission line may be used for any desired purposes, two typical uses of the microwave energy being illustrated in FIG. 1, the first use being illustrated in the upper righthand portion of FIG. l and the second use being illustrated in the lower portion of FIG. 1. Referring to the upper righthand portion of FIG. 1, in the first use of the microwave energy illustrated therein the transmission line 65 is coupled to an antenna of the type commonly used in search radar, the outer conductor 66 being connected to outer radiating or antenna elements 68 and the inner conductor 67 being connected to an inner radiating or antenna element 69, the antenna elements 68 and 69 serving to match the impedance of the transmission line 65 to the impedance of the atmosphere. Referring to the lower portion of FIG. 1, in the second use of the microwave energy illustrated therein the transmission line 65 is coupled to an electronic heating apparatus, such as the electronic range 70 illustrated that is generally designed for home use. More particularly, the range 70 comprises an upstanding s-ubstantially box-like casing 71 formed of steel and housing therein a metal liner 72 defining a heating cavity therefor. The metal liner 72 may also be formed of steel, and essentially comprises a boxlike structure provided with a top wall, a bottom wall, a rear wall and a pair of opposed side walls, whereby the liner 72 is provided with an upstanding front opening into the heating cavity defined therein, the casing 71 being provided with a front door 73 arranged in the front opening thus formed and cooperating with the liner 72. More particularly, the front door 73 is mounted adjacent to the lower end thereof upon associated hinge structure 74, and is provided adjacent to the upper end thereof with a handle 75, whereby the front door 73 is movable between a substantially vertical closed position and a substantially horizontal open position with respect to the front opening provided in the liner 72. Also the front door 73 has an inner metal sheet that is formed of steel and cooperates with the liner 72 entirely to close the heating cavity when the front door 73 occupies its closed position. For safety purposes, the inner liner 72 is connected by a conductor 76 to the outer casing 71 which is in turn grounded by the conductor N. The outer conductor 66 of the transmission line 75 is connected as at 78 to the casing 71 and to the liner 72 of the range 70, and there is provided within the range 70 at the rear thereof a radiating element or antenna 77 that is connected as at 79 to t-he inner conductor 67 of the transmission line 65. Accordingly, the microwave energy within the trans-mission line is radiated into the cooking cavity of the range to provide the power for cooking materials disposed therein. It further will be understood that in a preferred embodiment of the range 70, the power supply 50 and the oscillator 200 together with the transmission line 65 are all preferably disposed within a common housing that also includes the casing 71, the common housing being preferably formed of metal, such as steel, and grounded for safety purposes.

Further details of the construction of the oscillator 200 and the crossed-field discharge device forming a part thereof will now be described with particular reference to FIGS. 2 to l0 of the drawings. The device 100 comprises an anode structure 101 including a sleeve 102 and a pair of anode members 110 and 130, a cathode structure 150,

21'. pair of opposed pole pieces 170, and an end structure The anode structure 101 is essentially annular in shape and is confined within the interior of the sleeve 102 (see FIGS. 3, 4 and 5), the sleeve 102 being generally tubular and having a circular cross section at all points therealong, the outer surface 103 thereof being cylindrical. The inner surface 104 of the sleeve 102 is also cylindrical in shape and has at each end thereof a recess to define an upper end wall 105 and a lower end wall 106, the end walls 105 and 106 being essentially -annular in shape and disposed parallel to each other and normal to the axis of the device 100. Mounted on the outer surface 103 of the sleeve 102 is a stacked array of cooling fins 108, each of the cooling fins 108 being provided with an annular flange 109 that extends -around the sleeve 102 and is fixedly secured thereto as by brazing. It will be understood that the sleeve 102 and the fins 108 are formed of a metal having good thermal conductivity, the preferred material being copper, thereby to accommodate conduction of heat from the device 100 outwardly therefrom and into the fins 108. The shape of the fins 108 is substantially rectangular so that they fit within the casing 205, there preferably being provided means for passing a cooling fiuid, such as a stream of air, through the casing 205 and over the fins 108 to effect cooling thereof and a consequent removal of heat from the device 100 during the operation thereof.

Disposed within the sleeve 102 and also forming a part of the anode structure 101 are the two anode members 110 and 130. Referring particularly to FIGS. 3 and 7 to 10, there is illustrated in detail the construction of the anode member 110. As illustrated, the anode member 110 is generally annular in shape and includes a body portion 111 disposed at one end thereof (the upper end as viewed in FIG. 3), the body portion 111 having an outer end wall 112 at one end thereof connecting with an annular outer wall 113 having an outer diameter only slightly less than the inner diameter of the sleeve 102, and specifically the inner surface 104 thereof, whereby the anode member 110 can t within the sleeve 102 and ultimately is connected thereto as by brazing. The end of the body portion 111 opposite the end Wall 112 is cut away or recessed to provide an annular inner wall 114 extending therearound and concentric with the annular outer wall 113 but having a substantially smaller diameter, the walls 113 and 114 being joined by an annular end wall 115 disposed parallel to the outer end wall 112 and normal to the walls 113 and 114; the other end of the inner wall 114 connects with an inner end wall 116 that defines the other end of the body portion 111, the end wall 116 being disposed in a plane parallel to the end walls 112 and 115 and normal to the walls 113 and 114.

There is provided interiorly of the anode member 110 and extending the length of the body portion 111 a plurality of axially extending anode segments 117 that project radially inwardly into the axially extending space within the anode member 110 and provide therebetween a corresponding plurality of axially extending anode recesses 122, fifteen of the anode segments 117 and fifteen of the corresponding recesses 122 being provided in the anode member 110 as illustrated. Each of the anode segments 117 has an axially extending inner surface 118 and a pair of outwardly directed side walls 119 on the opposite sides thereof, the circumferential extent of the inner surface 118 being substantially less than the radial extent of the associated side walls 119. The outer ends of adjacent pairs of the side walls 119 are joined by an outer wall 121, whereby the recesses 122 are defined by the associated side Walls 119 and the associated outer wall 121, the side walls 119 of each recess 122 converging inwardly and being disposed substantially normal to the associated outer wall 121.

The anode member 110 further has thereon and integral therewith fifteen rods or vanes 125, each of the rods 125 being integral with and extending longitudinally from one of the anode segments 117. More specifically, the inner surface 118 of each of the anode segments 117 extends forwardly beyond the inner end wall 116 and substantially parallel to the axis of the anode member 110 and forms the inner surface of the associated rod 125. A portion of the side walls 119 on the anode segment 117 also extends forwardly beyond the inner end wall 116 to provide the radially extending sides of the associated rod 125, the inner surface 118 and the side walls 119 terminating at an end 126 disposed substantially normal to the axis of the anode member 110. An outer surface 127 is provided for each of the rods 125, the outer surface 127 extending from the inner end wall 116 inwardly to the rod end 126; more specifically, the outer end of the outer surface 127 joins the inner end wall 116 at a point spaced radially inwardly away from the adjacent outer walls 121 (see FIGS. 8 and 9), and tapers inward- 1y toward the associated inner surface from the end wall 116 to the rod end 126.

The anode member 130 is generally annular in shape and includes a body portion 131 disposed at one end thereof (the lower end as viewed in FIG. 3), the body portion 131 having an outer end wall 132 at one end thereof connecting with an annular outer wall 133 having an outer diameter only slightly less than the inner diameter of the sleeve 102, and specifically the inner surface 104 thereof, whereby the anode member 130 can fit within the sleeve 102 and ultimately is connected thereto as by brazing. The end of the body portion 131 opposite the end wall 132 is cut away or recessed to provide an annular inner wall 134 extending therearound and concentric with the annular outer wall 133 but having a substantially smaller diameter, the walls 133 and 134 being joined by an annular end wall 135 disposed parallel to the outer end wall 132 and normal to the Walls 133 and 134; the other end of the inner wall 134 connects with an inner end wall 136 that defines the other end of the body portion 131, the end wall 136 `being disposed in a plane parallel to the end walls 132 and 135 and normal to the walls 133 and 134.

There is provided interiorly of the lanode member 130 and extending the length of the body 131 a plurality of axially extending anode segments 137 that project radially inwardly into the axially extending space within the anode member 130 and providing therebetwen a corresponding plurality of axially extending anode recesses 142, fifteen of the anode segments 137 and fiften of the corresponding recesses 142 being provided in the anode member 130. Each of the anode segments 137 has an axially extending inner surface 138 and a pair of outwardy directed side walls 139 on the opposite sides thereof, the circumferential extent of the inner surface 138 being substantially less ythan the radial extent of the associated side walls 139. The outer ends of the side walls 139 are joined by an outer wall 141, whereby the recesses 142 are defined by the associated side walls 139 and the associated outer wall 141, the side walls 139 of each recess 142 converging inwardly and being disposed substantially normal to the associated outer wall 141.

The anode member 130 further has thereon and integral therewith fifteen rods or vanes 145, each of the rods 145 being integral with and extending longitudinally from one of the anode segments 137. More specifically, the inner surface 138 of each of the anode segments 137 extends forwardly beyond the inner end wall 136 and substantially parallel to the axis of the anode member 130 and forms the inner surface of the associated rod 145. A portion of each of the side walls 139 terminate at and end 146 disposed substantially normal to the axis of the anode member 130. An outer surface 147 is provided for each of the rods 145, the outer surface 147 extending from the inner end wall 136 inwardly to the rod end 146; more specifically, the outer end of the outer surface 147 joins the inner end wall 136 at a point spaced radially inwardly away from the adjacent outer `wall 141 and tapers inwardly toward the associated inner surface from the end wall 136 to the rod end 146.

The anode members 110 and 130 are also formed of a metal having good thermal conductivity, the preferred material being copper. The sleeve 102 and the anode members 110 and 130 also must have good electrical conductivity, the copper providing the necessary good electrical conductivity as well as the good thermal conductivity. The geometry of the anode members 110 and 130 is such that the exterior surfaces 112, 113, 114, 115, 116, 126 and 127 on the anode member 110 and the surfaces 132, 133, 134, 135, 136, 146 and 147 on the anode member 130 can all be formed by machining a block of copper; and all of the interior surfaces of the anode members 110 and 130 including the surfaces 118, 119, 121, 138, 139 and 141 can all be formed by broaching, whereby the anode members 110 and 130 can be formed integral from blocks of copper, thus to provide greater accuracy of the parts than is possible by jointing, such as by brazing, individual segments of the anode members 110 and 130. As illustrated in FIG. 3, the anode member 110 is disposed in the upper portion of the sleeve 102 with the body portion 111 thereof disposed upwardly and with the rods 125 lthereof extending downwardly; the anode member 130 is disposed in the lower portion of the sleeve 102 with the body portion 131 thereof disposed downwardly and with the rods 145 thereof extending upwardly. As is also illustrated in FIGS. 7 and 10, the anode members 110 and 130 are rotated slightly with respect to each other so that the anode rods 125 on the anode member 110 are disposed in the centers of the recesses 142 of the anode member 130, and conversely the anode rods 145 on the anode member 130 are disposed in the centers of the recesses 122 of the anode member 110. In this arrangement, there is one of the anode rods 12S disposed in each of the anode recesses 142 and equidistantly spaced from the adjacent anode segments 137, and likewise there is one of the anode rods 145 disposed in each of the anode recesses 122 and equidistantly spaced from the adjacent 8 anode segments 117, all as it diagrammatically illustrated in FIGS. 5, 7 and l0.

The sleeve 102 and the anode members 110 and 130 also cooperate to provide an outer axially extending space 120, the space being annular in shape and bounded on the outer portion by the inner wall 104 of the sleeve 102 and on the inner portion by the inner walls 114 and 134 and at the upper and lower ends by the end walls 115 and 135. The interior of the anode members 110 and 130 form a second or inner axially extending space within which is disposed the cathode structure 150, the space between the outer surface of the cathode structure 150 and the facing surfaces 118 and 138 defining an annular axially extending interaction space 160.

- Furthermore, the inner end walls 116 and 136 are spaced apart to provide therebetween a radially extending annular passage interconnecting the outer space 120 at the mid-portion thereof to the inner axially extending space at the mid-portion thereof and to the interaction space 160 at the mid-portion thereof.

The cathode structure is provided in the axially extending space defined by the anode members 110 and 130, the cathode structure 150 including a cylindrical metal wall 151 (see FIGS. 3 4and 5) arranged with the axis thereof disposed at the axis of the device 100, the wall 151 being formed of a heat resistant and electrically conducting metal, the preferred material of construction being nickel. Mounted on the lower end of the wall 151 is a cathode end 152, .the cathode end 152 including a substantially fiat annular center plate 153 carrying on the outer edge thereof an axially directed annular inner fiange 154 secured to the wall 151 as by welding and .carrying on the outer end thereof a plurality of tangs 154a mounting a circular end shield 155 thereon with the outer edge of the shield 155 overlying the adjacent end of the interaction space 160. The center plate 153 has a central opening therein receiving a bushing 156 therethrough and secured thereto. The cathode end 152 and the end shield 155 are also preferably formed of nickel. The upper end of the cathode wall 151 carries an annular end plate 157 disposed therein and secured thereto as by welding, the opening in the center of the end plate 157 being surrounded by an annular conductor 158 secured thereto as by welding and extending upwardly therefrom. Mounted on the conductor 158 and extending therearound is an end shield 159 including a mounting flange 159a surrounding the conductor 158 and secured thereto Vas. by welding and an outer annular ange 1S9b overlying the outer periphery of the interaction space 160. Preferably the end plate 157 and the conductor 158 and the end shield 159 are all formed of nickel.

The cathode wall 151 is provided with a sintered porous coating 161 impregnated with a suitable electron emissive oxide material, whereby upon heating of the cathode structure 150, :the coating 161 readily emits electrons from the outer surface thereof. Referring particularly to FIG. 5, it will be seen that the coating 161 is shaped to provide a plurality of outwardly extending projections 162 each having outwardly converging side walls joining a generally circumferentially arranged outer surface 163, a space `164 being provided between the adjacent projections 162. As illustrated, the circumferential extent of the outer surface 163 is substantially equal to the circumferential extent space 164 between the adjacent projections 162. The preferred range of the circumferential extent of each of the outer surfaces 163 is approximately 25% to approximately 60% of the circumferential distance between the centers of adjacent outer surfaces 163. The number of projections 162 provided on the coating 161 is equal to the sum of the number of the anode segment 117 land the number of cooperating rods 145, for example, and is likewise equal to the sum of the number of the anode segments 137 and the number of two cooperating rods '125, whereby there are thirty of the projections 162 provided upon the coating 161. The

outer surfaces of the coating 161 together with the inner surfaces 118 and 138 on the anode members 110 and 130, respectively, define the interaction space 160 disposed therebetween in which the emitted electrons from the coating 161 interact with the electrical fields and the magnetic fields disposed ybetween the anode structure 101 and the cathode structure 150. As will be described more fully hereinafter, the projections 162 combine with the anode segments '117 and 137 and with the rods 125 and 145 to provide a preferred distribution of the several fields within the interaction space 160 of the device 100 that results in more desirable operating characteristics thereof. One particularly desirable result of the shape of the coating 161 is the minimized `back heating of the cathode structure 150, the desirable emitted electrons emanating from the projections 162, and the undesirable emitted electrons emanating from the spacer 164 between the projections 162, thereby to facilitate the emission of desirable electrons and to suppress the emission of undesirable electrons.

It further will be noted from FIG. that the center line of each projection 162 is circumferentially displaced relative to the center line of its corresponding anode -segment 117 and 137 or its corresponding rod 125 and 145, as the case may be; more specifically, the center line of the projections 162 are displaced in a clockwise direction a circumferential distance equal to approximately 40% of the circumferential spacing between the center lines of an adjacent anode segment 117 and an adjacent rod 145 (for example 5 rotation for a 12 spacing or a percentage of 41.8% as illustrated). The circumferential displacement of the projections 162 with respect to the corresponding anode segments or rods is preferably in the range between 0% and approximately 45% of the circumferential spacing between adjacent anode segments and rods, the preferred range being between approximately and 45% of the spacing between adjacent anode segments and rods, a still more preferred range being between approximately and 45% of the spacing between adjacent anode segments and rods. Furthermore, the displacement is on the downstream side, i.e., in the direction of normal initial electron flow from the projections 162. It also will be noted that the electron emissive coating 161 is confined between the outer end walls 112 and 132 of the anode members 110 and 130, respectively, the cathode structure 150 being carefully centered with respect to the anode members 110 and 130, whereby each of the cathode projections '162 extends axially of the device 100 parallel to the axis thereof and confined between the outer end walls 112 and 132. The radial dimension of each of the projections 162 is preferably greater than about 20% of the spacing between the anode surfaces 118 and 138 and the coating 161 on the cathode structure 150.

As illustrated, the cathode structure 150 is of the indirectly heated type, and accordingly, there has been provided within the cathode wall 151 a heater 176 in the form of a coiled filament extending substantially the entire length of the cathode vwall 151 and spaced inwardly a short distance from the inner surface thereof. The upper end of the heater 176 as viewed in FIG. 3 has an outer end or terminal 177 that extends outwardly through an opening in an insulator 181 and is mechanically and electrically connected to the lower end of a tubular inner conductor 195 extending upwardly therefrom. The lower end of the heater 176 has an outer end or terminal 178 that extends through an opening in the bushing 156 and is mechanically and electrically secured thereto and to the lower end of the cathode wall 151.

Mounted within the outer ends of the anode sleeve 102 and forming end walls for the device 100 are the pole pieces 170, the pole pieces 170 being identical in construction, whereby the same reference numerals have been applied to like parts of both of the pole pieces 170.

The pole pieces 170 are formed of a material having high magnetic permeability, the preferred material being a low carbon steel, `and are copper plated to render the outer surfaces thereof highly conductive to RF energy. As illustrated, each of the pole pieces 170 is generally annular in shape including a first substantially flat inner plate 171 disposed centrally thereof and disposed in a plane substantially normal to the longitudinal axis of the device and in longitudinal alignment with the interaction space 160. Disposed about the periphery of the inner plate 171 and integral therewith is an annular coupling flange 172 extending outwardly therefrom and carrying on the outer edge thereof an outwardly directed outer plate 173 that is substantially flat and lying in a plane normal to the axis of the device 100 and being in longitudinal alignment with the adjacent end of the outer axially extending space 120. The outer edge of the outer plate 173 carries an annular and outwardly eX- tending mounting flange 174 that has an outer diameter slightly less than the inner diameter of the associated recessed end of the `anode sleeve 102 to be received therein and hermetically sealed thereto. Finally, there is provided centrally of each of the inner plates 171 a circular opening 175 in general longitudinal alignment with the adjacent end of the cathode wall 151, the opening 175 receiving the terminals of the cathode structure and heater therethrough. Preferably the pole pieces 170 are each formed of a single sheet of low carbon steel shaped as described by a stamping operation, thereby to provide accurate dimensions therefor together with inexpensive manufacture thereof.

The lower end of the device 100 is hermetically sealed by an exhaust tubulation 107 mounted on the lower pole piece 170 and the upper end of the device 100 is hermetically sealed by an end structure 180. More specifically, the exhaust tubulation 107 has on the upper end thereof an annular flange 107a extending therearound and overlying the inner plate 171 of the lower pole piece 170 and surrounding the opening 175 therein, the fiange 107:1 and the inner plate 171 being hermetically sealed and interconnected as by welding. It will be seen that the exhaust tubulation 107 communicates with the interior of the device 100, the eX- haust tubulation 107 being useful to evacuate the device 100, the interior of the device 100 being evacuated to a high degree and hermetically sealed.

The upper structure 180 provides a hermetic seal between the upper pole piece 170 and the connections to the cathode structure and the yheater 176 and includes the insulator 181 disposed in the opening in the annular end plate 157, the lower end of the insulator 181 having a radially outwardly extending flange 182 thereon that extends outwardly beyond the adjacent edge of the opening in the annular end plate 157. The upper surface of the flange 182 carries a plate 183 thereon, the plate 183 in turn carrying a getter 184 during the construction of the device 100 and until the firing of the getter. It will be seen that the insulator 181 is formed of a good electrically insulating material, such as a ceramic, whereby the insulator 181 serves mechanically to mount the heater terminal 177 in a fixed relationship to the conductor 158 and insulated therefrom. Surrounding the conductor 158 and the opening 17S in the upper pole piece is a second insulator 186, preferably formed of a good electrical insulating ceramic, a first hermetic seal being made between the pole piece 170 and the insulator 186 by means of an annular seal member 187, and a second hermetic seal being made between the upper end of the insulator 186 and the conductor 158 by means of an annular seal member 188 and an annular sealing ring 189. It is pointed out that the various sealing members 187, 188 and 189 are formed of a material that can be readily secured both to a metal surface and to a ceramic surface, the preferred material being Fernico alloya typical composition being 54% iron, 28% nickel and 18% cobalt. It will be seen that the upper end structure 180 forms a good hermetic seal that also provides electrical insulation between the upper pole piece 170 and the conductor 158 and between the conductor 158 and the conductor 195, the end structure 180 likewise providing the necessary mechanical support for the cathode structure 150 and for the heater 176 and to position them within the anode structure 101.

From the above description of the parts, it will be appreciated that the conductor 158 is commonly electrically connected both to the cathode wall 151 and to the lower terminal 178 of the heater 176, whereas the conductor 195 is connected only to the upper terminal 177 of the heater 176 and is disposed within the annular conductor 158. By this construction, the heater 176 is completely shielded from RF energy by the cathode 151 and by the lower cathode end 152 and by the end plate 157 and the conductor 158; likewise, the upper terminal 177 thereof and the associated conductor 195 are completely shielded from RF energy by the conductor 158 and the connected parts.

Finally, there is provided around the upper end of the conductor 158 .an annular outer conductor 190 that is both mechanically and electrically secured thereto, the conductor 190 preferably being formed of copper. Disposed in the upper end of the conductor 158 is an insulator 191, preferably formed of a good electrical insulating ceramic, the insulator 191 fitting within the upper end of the conductor 158 and having a laterally outwardly extending ange 192 overlying the upper end thereof and hermetically sealed thereto. An opening centrally of the insulator 191 receives therethrough the inner conductor 195, also preferably formed of copper, an hermetic seal being provided between the insulator 191 and the conductor 195. It will be seen therefore that the outer conductor 190 is connected electrically both to the cathode 150 and to one end of the heater 176, while the inner conductor 195 is connected only to the other terminal 177 of the heater 176.

When the device 100 is incorporated as a crossed-field discharge device in a microwave circuit, the pole pieces 170 arranged adjacent to the opposite ends of the anode structure 101 are utilized for establishing a unidirectional magnetic eld extending axially through the several spaces within the anode structure 101, and specifically through the axially extending space 120 and through the interaction space 160, as well as the annular passage 140 and the various spaces between the anode members 110 and 130. To this end a pair of magnet coils 210 and 215 has been provided, the magnet coil 210 being disposed about the upper end of the device as viewed in FIG. 2 and the magnet coil 215 being disposed about the lower end of the device 100 as viewed in FIG. 2. The magnet coils 210 and 215 are both shaped as a torus, are wound of electrically conductive wire, and as illustrated, are disposed respectively about magnet yokes 211 and 216, respectively, that are each in the form of a cylinder disposed within the opening in the associated magnet coil. There further are provided outwardly extending flanges 212 and 27, respectively, about the outer ends of the magnet yokes 211 and 216 and secured respectively thereto, the casing 205 being disposed within the flanges 212 and 217, respectively, and forming both a mechanical connection and a good magnetic path therebetween. It will be understood that the pole pieces 170, the magnet yokes 211 and 216, the flanges 212 and 217 and the casing 205 are all formed of metals having a high magnetic permeability, such as soft iron and low carbon steel, whereby when the magnet coils 210 and 215 are energized, a strong and uniform unidirectional magnetic -field is established between the pole pieces 170 within the device 100 and extending axially through the spaces within the device 100 and specically extending axially through the outer axially extending space 120 and the interaction space 160 therein.

The circuit for energizing the coils 210 and 215 can be traced with reference to FIGS. 1 and 2 from the power supply 51, and specifically the DC output terminal 54 thereof, through the conductor 60 to the input terminal 201 of the oscillator 200 to which is connected one terminal of the upper magnet coil 210. The other terminal of the upper magnet coil 210 is connected by a conductor 213 to one terminal of the lower magnet coil 215, and the other terminal of the lower magnet coil 216 is connected by a conductor 218 to one of the cooling fins 108 by means of a connection 219, whereby the input terminal 201 is connected via the upper magnet coil 116, the conductor 213, the lower magnet coil 215, the conductor 218 and the cooling n 108 to the anode sleeve 102 of the device 100. The flow of current through the magnet coils 210 and 215 serves to produce the unidirectional magnetic lfield in the various spaces of the device and specifically in the outer space and the interaction space thereof.

Referring now to FIG. 2 of the drawings, the manner in which the cross-field discharge device 100 is incorporated in the oscillator 200 will be descirbed in further detail. A tubular conductor 207, preferably formed of copper, is provided having the lower end thereof received within the upper pole piece coupling ange 172 in telescopic relation therewith and electrically connected thereto, the conductor 207 also being disposed within the upper magnet yoke 211 and extending up to the magnet flange 212. As illustrated, the conductor 190 is connected to the cathode 150 and to one terminal of the heater 176 as well and the inner conductor 195 is connected to the other terminal of the heater 176 and both conductors 190` and 195 extend upwardly and beyond the magnet flange 212. The annular conductor 190 and the annular conductor 207 form a coaxial transmission line that provides output terminals for the oscillator 200, the terminals having applied thereto the output RF energy from the oscillator 200. In addition, the outer conductor 207 has applied thereto the B+ potential from the conductor 60 which is connected via the input terminal 201, the upper magnet coil 210, the conductor 213, the lower magnet coil 215, the conductor 218, the cooling -iin 108 to which is made the connection 219, the anode sleeve 102 and the upper pole piece 170, the upper pole piece being directly connected to the lower end of the outer conductor 207 as illustrated. Accordingly, it ywill be seen that the outer conductor 207 not only serves as one of the 'RF output terminals for the device 100 "but also is in direct electrical connection with the -B+ potential on the anode sleeve 102. Likewise, the cathode conductor 1-90 not only has the RF output energy therein but has applied thereto both the B potential for the cathode 150 and the low voltage AC potential for energizing the heater 176.

In order to accommodate the application to and the presence of the various potentials named on the output terminals and 207 as well as the AC potential on the conductor while preventing the introduction of RF energy into the power supply 51, and while preventing the application of the B1L and B- potentials to the output transmission line 65, there is provided an improved coupler and iilter structure 220. Referring to FIG. 2, it will be seen that the coupler and lter structure 220 includes a T 221, preferably formed of copper, and including a lower annular arm 222 having in longitudinal alignment therewith an upper annular arm 223 and a side annular arm 224 disposed substantially normal to the axes of the arms 222 and 223. The lower arm 222 is telescopically received within the upper end of the conductor 207 and is electrically and mechanically connected thereto and forms in essence a continuation thereof. The annular conductor 190 extends upwardly through the arms 222 and 223 and beyond the upper end of the arm 223, and the inner conductor 195 extends upwardly the entire length of the annular conductor 190 and beyond the upper end thereof. Disposed within the upper arm 223 and telescopically received therein is a iilter 225 including an annular conductor 226 disposed within the arm 223 and telescopically associated therewith, an insulating sleeve 229 being disposed therebetween to provide electrical insulation, the sleeve 229 preferably being formed of a synthetic organic resin, the preferred resin being polytetrafluoroethylene resin sold under the trademark Teonf The outer end of the conductor 226 is closed by an end wall 227 having an opening centrally thereof receiving the conductor `190 therethrough, a ange 228 being formed integral with the end wall 227 and surrounding the conductor 190 and mechanically and electrically secured thereto. The telescoping portions of the arm 223 and the iilter conductor 226 overlap a distance equivalent to 14 wavelength of the frequency of the device 100, thereby to prevent propagation of RF energy therefrom. The flange 228 preferably has the conductor 461 connected thereto as to 202 to provide the input terminal 202 of the oscillator 200 and the portioin of the conductor 195 extending beyond the upper end of the conductor 190 has the conductor 62 connected thereto as at 203 to provide the input terminal 203 for the oscillator 200. Finally, an insulator 230 is provided in the upper end of the conductor 190` and has an opening therein to receive the conductor 1-95 therethrough, the insulator 230 including a cylindrical body 231 disposed within the conductor 190 and a radially outwardly extending flange 232 overlying the upper end of the ange 228, whereby the insulator 230'serves to center the conductor 195 within the conductor 190 and to provide electrical insulation therebetween.

The RF energy from the device 100 is directed into the side arm 224 of the T 221 and to this end there has been provided about the conductor 190 opposite the arm 224 a bushing 234 formed of copper, the bushing 234 being xedly and electrically secured to the conductor 190. Mounted on the bushing 234 and extending therefrom and into the side arm 224 is a probe 235, one end of the probe 235 being threaded as at 236 and received in a threaded opening in the bushing 234 to be supported thereby and electrically connected thereto. Within the side arm 224 there is provided an annular insulator 237, preferably formed of Teon, completely Ifilling the area between the probe 235 and the interior of the side arm 234, the insulator 237 abutting on the left thereof against a shoulder 238 in the side arm 224 and being held in place therein by an annular conductor 239 disposed within the side arm 224 and iixedly secured thereto as by brazing.

There is capacitively coupled to the annular conductor 239 an outer conductor 240 telescopically arranged therearound and having disposed therebetween the insulating sleeve 241 which serves to provide a capacitive coupling M2 between the conductors 239 and 240 for RF energy transfer therebetween while providing a DC insulation therebetween. There also is provided in telescopic relation with the probe 235 an annular conductor 245, an electrically insulating sleeve 246 being disposed therebetween to provide a capacitive coupling 247 for the transfer of RF energy from the probe 235 to the inner conductor 245 while providing DC insulation therebetween. The inner conductor 245 is disposed within the outer conductor 240 to form a coaxial transmission line which is the output from the output coupler and lfilter structure 220, the conductors 240 and 245 comprising the output terminals for the coupler 220. Preferably the insulating sleeves 241 and 246 are formed of a synthetic organic plastic resin, the preferred resin being a polytetrailuorethylene resin sold under the trademark Teflon.

The outer conductor 240 telescopically overlaps the conductor 239 a distance equal to 1A wavelength of the frequency of operation of the oscillator 200, and the inner conductor 245 telescopically overlaps the probe 235 a distance equal to 1A wavelength of the frequency of operation of the oscillator 200; as a result the capactive couplings 242 and 247 not only serve to feed the RF energy to the coaxial transmission line formed by the conductors 240 and 245, but the described cooperation of the parts provides a rejection filter for the second and higher harmonics of the operating frequency of the oscillator 200, whereby to iilter the second and higher harmonics from the out-put of the coupler 220, i.e., to prevent propagation of the second and higher harmonics along the output coaxial transmission line comprising the conductors 240 and 245. As is illustrated in FIG. 1, the conductor 245 is connected to the inner conductor 67 and the outer conductor 240 is connected to the outer conductor 66 of the transmission line 65, thereby to transfer RF energy thereto from the oscillator 200.

During the operation of the cross-field discharge device in the oscillator 200, the anode sleeve 102 and the anode members and 130 cooperate to provide a folded coaxial transmission line within the device 100, the coaxial transmission line thus formed accommodating axially extending RF waves therein and providing a frequency determining folded resonant cavity for the device 100 and for the oscillator 200. The coaxial transmission line more specifically includes an outer coaxial transmission line defined by the inner annular surface 104 on the sleeve 102 disposed between the annular end walls 115 and 135 on the anode members 110 and 130, respectively, and the annular inner walls 114 and 134 on the anode members 110 and 30, respectively; the portion of the outer surface 104 provides an outer conductor and the inner Walls 114 and 134 provided inner conductors for the outer coaxial transmission line, the outer coaxial transmission line being coterminous with the axially extending space and being shorted at the upper end by the wall 115 and at the lower end by the wall 135. The anode segments 117 on the rst anode member 110 and the rods 145 on the second anode member cooperate to provide a irst portion of an inner coaxial transmission line for accommodating an axially extending RF wave therein, the upper end of this inner coaxial transmission line being open and the lower end connecting through the passage 140 with the midpoint of the outer transmission line 120. In a like manner, the anode segments 137 on the second anode member 130 and the rods 125 on the first anode member 110 cooperate to provide a second portion of an inner coaxial transmission line for accommodating an axially extending RF wave therein, the lower end of the second portion of the inner coaxial transmission line being open and the upper end being connected by the passage 140 to the midpoint of the outer coaxial transmission line 120.

In the operation of the device 100, the upper portion of the outer transmission line 120, i.e., the portion between the end wall 115 and the passage 140 cooperates with the first or upper section of the inner transmission line to provide a resonant cavity which can be excited to cause oscillations therein at a frequency equal substantially to four times the length thereof, i.e., four times the distance from the end wall 115 down and through the passage 140 and upwardly along the rods 145 to the upper ends thereof, whereby to provide an axially extending `wave therein which is reflected by the end wall 115 at one end and by the open end of the transmission line at the other end to produce a standing RF wave. The lower portion of the outer transmission line 120, i.e., the portion between the end wall and the passage cooperates with the second or lower section of the inner transmission line to provide a resonant cavity which can be excited to cause oscillations therein at a frequency equal substantially to four times the length thereof, i.e., four times the distance from the end wall 135 up and through the passage 140 and down and along the rods 125 to the lower ends thereof, whereby to provide an axially extending wave therein which is reliected by the end wall 135 at one end and by the open end of the transmission line at the other end to produce a standing RF wave. The two transmission lines thus described actually cooperate in the operation of the device 100, and

more specifically, when an axial RF wave is excited on the inner transmission line, this RF wave is transmitted to thel outer transmission line through the passage and becomes reflected by the end walls 115 and 135. The reflected wave travels down toward the passage 140 and therethrough and then fiows oppositely toward each end of the inner transmission line. When the RF wave reaches the open circuited ends of the inner transmission line, refiections again occur and a standing wave is established providing RF electric fields and RF magnetic fields extending into the interaction space 160. It will be seen therefore that the device 100 includes a folded resonant cavity equivalent to a one-half wave resonator disposed in generally a 1/4 wave space, whereby to provide a device having small physical dimensions relative to the wavelength of the microwave energy to be generated thereby.

In the operation of the oscillator 200, it is necessary to produce within the crossed-field discharge device 100 a predetermined pattern of electrical fields and magnetic fields. The operating potentials for the device 100 are derived from the power supply 51 described above, and more particularly, the heater supply is derived from the power supply output terminals 56 and 57, the terminals 56 being connected by the conductor 61 to the terminal 202 that is in turn connected by the conductor 190, the conductor 158 and the end plate 157 to the cathode wall 151, the cathode wall 151 also being connected at the lower end thereof to the lower terminal 178 of the heater 176; the terminal 57 is connected by the conductor 62 to the terminal 203 which is connected by the conductor 195 to the other terminal 177 of the heater 176. The DC potential from the power supply 51 is derived specically from the output terminals 54 and 55, the conductor 60 interconnecting the output terminal 54 of the power supply 51 to the input terminal 201 (see FIG. 2 also) which is connected via the upper magnet coil 210, the conductor 213, the lower magnet coil 215, the conductor 218 and the fin 108 to the Outer anode sleeve 102 to supply B+ potential thereto, and the conductor 61 interconnecting the output terminal 55 of the power supply 51 to the terminal 202 which is connected via the conductor 190, the conductor 158 and the end plate 157 to the cathode to supply B- potential thereto.

The application of the above described B+ and B potentials to the outer anode sleeve 102 and the cathode 150, respectively, establishes the required unidirectional electrical field between the anode structure 101 and the cathode structure 150, and after the initiation of ow of current through the magnet coils 210 and 215 also establishes the unidirectional magnetic field axially of the device 100. The establishment of the unidirectional electrical and magnetic fields in the device 100 causes oscillation therein with the resultant establishment of an axially extending RF Wave therein having associated therewith RF electrical fields and RF magnetic fields normal to each other and normal to the axis of the device 100. A description of these various fields and a more full description of the manner of creating these fields is set forth in the copending application of James E. Staats, Ser. No. 559,267 led June 21, 1966, wherein is described a crossed-field discharge device 100 that operates in a manner like that of the crossed-field discharge device 100 of the present invention.

As may be best seen in FIG. 3, the cathode 150 is coupled to an axially extending standing wave within the interaction space and thereby serves as a probe for the removal of a portion of the RF energy from the tuned cavity for the supplying thereof to the coupler and filter structure 220 and thence to the output transmission line 65. In the structure illustrated, the conductor 158 is directly connected to the cathode structure 150 and the outer conductor 207 is directly connected to the upper pole piece 170, whereby an output RF potential appears therebetween. The coupler and filter structure 220 serves 16 to connect the RF energy between the conductors 158 and 207 to the output transmission line 65, and also to apply to the cathode 150 via the conductor 195 and the terminal 202 the B* operating potential and the low voltage AC from the conductor 61 connected to the power supply 51, all without applying DC operating potentials to the conductors 66 and 67 of the transmission line 65 and without the introduction of RF energy into the power supply 51 via the conductor 61.

Referring to FIG. 2, the operation of the coupler and filter structure 220 will be further described. The output terminals including the conductor 190` and the conductor 207 connected respectively to the cathode 150 and the upper pole piece of the device 100 also serve as RF input terminals to the coupler and filter structure 220, thereby to connect the oscillator 200 that serves as a source of RF potential to the RF input terminals of the filter structure 220. The -RF input terminals 207 and are capacitively coupled respectively to a pair of output terminals for the coupler and filter structure 220 in the for-m of the outer conductor 240 and the inner conductor 245, respectively, whereby to insure that the DC, B+ and B- potentials on the conductor 207 and the conductor 190, respectively, are not coupled to the output RF terminals 240 and 245, respectively. More specifically, the capacitive coupler 242 in the form of an insulating sleeve 241 provides a good RF coupling between the conductor 207 via the T 220 and the conductor 240 while preventing any DC connection therebetween. Likewise the probe 235 connected to the conductor 190 is capacitively coupled by the coupler 247 to the output conductor 245 while preventing any DC connection therebetween.

As has been explained above, the conductors 239 and 240 are preferably telescoped and overlapped a distance equivalent to 1A wavelength of the frequency of the oscillator 200, and likewise the probe 23S and the conductor 245 are telescoped and overlapped a distance equal to 1A wavelength of the operating frequency of the oscillator 200. By so arranging the parts, the capacitive couplers 242 and 2-47 serve not only to couple the 1RF energy to the conductors 240 and 245, respectively, but also serve as filters for the second and higher harmonics of operating frequency of the oscillator 200, thereby to attenuate and materially to reduce the amount of second and higher harmonics coupled to the RF output terminals provided by the coaxial conductors 240 and 245.

The -DC B potential on the conductor 61 is directly connected to the cathode 150 via the conductor 1-90 to the conductor 158 and the end plate 157 (see FIG. 3 also). The same connection also applies the low voltage AC heater supplied to the lower end of the heater 176. In order to prevent the propagation of the RF energy from the oscillator 200 into the conductor 61, the choke 225 has been provided, the overlapping portions of the choke conductor 226 and the upper arm 223 having a length equal to 1A wavelength of the operating frequency of the oscillator 200. The choke is shorted at the outer end thereof by the end wall 227 and in cooperation with the capacitive insulator 229 serves to prevent propagation of the RF energy from the oscillator 200 along the flange 228 and into the terminal 202 and the attached conductor 61. Due to the arrangement and dimensions of the parts a parallel resonant circuit having a high impedance at the frequency of operation of the oscillator 200 is provided, thereby to block the propagation of the IRF energy into the conductor 61.

As has been explained above the RF wave within the oscillator 200 extends axially with respect to the device 100, there being no radial RF Waves within the device 100, i.e., no IRF waves extending normal to the axis of the device 100. Furthermore, the radial distance between the outer surface of the cathode 150 and the outer walls 121 and 141 of the anode recesses 122 and 142, respectively, is less than that required to accommodate a radial standing wave at the operating frequency of the oscillator 200. Likewise, the distance between the facing coaxial surfaces 17 of the sleeve 102 and the anode members 110 and 130 defining the outer transmission line is less than that required to accommodate a radial standing wave at the operating frequency of the device 100 as defined above.

In a constructional example of the crossed-field discharge device 100, the various parts thereof have the following dimensions. The anode sleeve 102 has an external diameter of 1.69 inches, and an overall length of 2.625 inches. The anode members 110 and 130 at the walls 113 and 133 have an external diameter of 1.57 inches, an overall length from the outer end walls 112 and 132 to the rod ends 126 and 146 of 1.25 inch, a distance from the longitudinal axis to the surfaces 118 and 138 of 0.371 inch, a distance from the longitudinal axis to the surfaces 121 and 141 of 0.562 inch, a radial dimension of the recesses 122 and 142, of 0.191 inch, a circumferential dimension of the recesses 122 and 142 of 0.154 inch, a circumferential dimension of the surfaces 118 and 138 of 0.05 inch; a longitudinal dimension of the annular outer walls 113 and 133 of 0.314 inch, a longitudinal dimension of the annular inner walls 114 and 134 of 0.288 inch, and an external diameter of the inner walls 114 and 134 of 1.312 inches. The rods 125 and 145 have a length of 0.648 inch, a radial dimension at the base thereof of 0.125 inch, and a radial dimension at the outer ends thereof of 0.055 inch. The cathode structure 150 has a length of the emissive coating 161 of 1.22 inches, and a diameter 0.632 inch; the projections 162 have a radial extent of 0.031 inch; the outer surfaces 163 on the projections 162 have a circumferential extent of 0.031 inch and the spaces 164 therebetween have a circumferential extent of 0.031 inch; and the angular displacement between the center line of a cathode projection 162 and the center line of the adjacent anode segment 117 or 137 or the adjacent rod 125 or 145 is 5. The pole pieces 170 have an overall outer diameter at the mounting flange 174 thereof of 1.688 inches, an inner diameter at the coupling flange 172 of 1.12 inches, a longitudinal extent of the mounting ange 174 of 0.25 inch and a longitudinal extent of the coupling iange 172 of 0.25 inch. The foregoing dimensions are for a crossed-field discharge device 100 operating in the general frequency range 900 to 980 megacycles.

From the above description and particularly the dimensions of the illustrative example of the device 100, it will be seen that the physical dimensions thereof are very small compared to the wavelength of the microwave energy to be generated thereby and the power output therefrom. The thermal characteristics of the device 100 are excellent, the eects of thermal expansion of the parts being minimized resulting in an improved thermal stability. It will be understood that external cooling'may be provided by means of a clamp-on radiator or cooling coil in lieu of the stacked array of cooling iins 108 illustrated. The anode members 110 and 130 are both constructed from a good heat conducting material and the thick radially extending portions thereof oifer a very low thermal resistance thus permitting high power operation. The cantilever mounting of the rods 125 and 145 also contributes to the thermal stability ofthe device 100 since the major dimension thereof is axially of the tube, whereupon expansion of the rods 125 and 145 does not materially alter the spacing thereof with respect to the inner anode members 110 and 130 and the cathode structure 150.

The described construction of the device 100 further provides very large mode separation during operation thereof as an oscillator, since a single cavity of the type provided gives principal modes such as 1/4, 5A, 5A, etc. wavelengths having substantial mode separation. Rotating waves present in conventional magnetrons are-highly attenuated in the device 100, the absence of such rotating Waves being highly desirable since in conventional magnetrons such rotating waves produce a large number of modes which are not widely separated even with very heavy strapping, thereby to provide problems of mode separation. In the device on the other hand, the ratio of the path for RF waves along the inner diameter of the sleeve 102 (i.e. the diameter of the surface 104) to the path for RF waves along the inner surface of the anode members and 130 (i.e., along the surfaces 118, 119 and 121 or 138, 139 and 141, as the case may be) is small, whereby to provide a short and low impedance path for rotating waves; more specifically, the electrical surfaces 104 and 114-134 provide a very low impedance transmission line for rotating RF waves, and by contrast the path of rotating waves along the inner periphery of the anode members 110 and 130 in sinuous and long as is the path for rotating waves along the surface of the cathode whereby to improve mode separation and stability in the device 100. Furthermore, the facing surfaces 116 and 136 on the anode members 110 and 130, respectively, also provide a short and low impedance path for rotating RF waves, thus improving mode separation and stability in the device 100. Mode stability is also improved due to the tapered structure of the vanes or rods 125 and 145, this shape of the rods 125 and 145 tending to reduce the capacitance between the rods and the adjacent anode segments 117 and 137, respectively, thereby to provide a capacitance therebetween that is reduced relative to the capacitance presented by the outer transmission line 120.

The tapered rods 125 and 145, and the reduced capacitance thereof With respect to the adjacent anode members and anode segments, also results in lower circulating current and the consequent greater circuit efliciency. Such a tapered shape of the rods 125 and 145 also provides for a reduced phase shift of the RF voltages at the outer ends thereof relative to the junction thereof with the attached anode member 110 or 130, as the case may be, thereby to result in improved electron bunching and consequent improved electronic etliciency during the operation of the device 100. More specifically, it has been found that the provision of the tapered rods 125 and 145 can increase the power output 20% and the maximum current rating 15% as compared to rods having a uniform cross section from end to end thereof.

It also has been found that the cathode coupling de scribed above is very tight so that the resonant cavity within the device 100 may be heavily loaded for low Q, broad band operation which permits external tuning of at least ten percent. In addition the cathode coupling couples the energy from the device 100 uniformly around the interaction space so that pattern distortion due to loading is avoided with a resultant increase in the eciency of operation and stability of operation.

In connection with the coupling of RF energy from the device 100, it is pointed out that the end space regions between the ends of the anode members 110 and 130 and the pole pieces dene an inductance of predetermined value, the inductance being directly proportional to the volume of the spaces between the anode members 110- 130 and the pole pieces 170. By adjusting the volume of these end space regions, the desired degree of output coupling can be obtained, a tight coupling being shown in the drawings, an increase in the volume by increasing the spacing between the anode members 110-130 and the pole pieces 170 loosens the coupling, and conversely, a decrease in the volume by decreasing the spacing between the anode members 110-130 and the pole pieces 170 tightens the coupling.

The described construction of the several parts of the device 100 permits complete assembly of the tube prior to brazing of the several parts so that the cathode is converted during the brazing process; this permits a faster bake out of the cathode and a shorter processing cycle for the evacuation of the interior of the device 100. Another resultant advantage is that the parts are subject to cleaning by hydrogen in the brazing process and are not exposed to subsequent contamination in later processing steps. In this connection it also is pointed out that the inner surfaces of the outer ends of the sleeve 102 that are 19 to be joined to the mounting anges 174 on the pole pieces 170 are silver plated which permits brazing therebetween without internal fixturing, and thus allows complete assembly of the tube parts prior to brazing thereof.

There is shown in FIGS. l1 and 12 of the drawings a modified form of the oscillator circuit and specifically an improved oscillator circuit 400. The oscillator 400 incorporates therein a crossed-field discharge device 300 that is identical in construction to the crossed-field discharge device 100 described above, whereby numerals in the 300 series have been applied to the parts of the device 300 that correspond to like numbered parts in the 100 series of the device 100. Likewise, the output from the crossedfield discharge device 300 is coupled to an output coupler and filter structure 420 that is identical in construction to the output coupler and filter structure 220, whereby numerals in the 400 series have been applied to the parts of the coupler and filter structure 420 that correspond to like numbered parts in 200 series of the coupler and lter structure 220.

There further is provided about the annular outer surface 303 of the anode sleeve 302 a pair of cylindrical sleeves 450 and 455 that fit closely around the anode sleeve 302 and extend longitudinally outwardly beyond the associated outer ends thereof. More specifically, the cylindrical sleeve 450 has a reduced portion 451 on the inner end thereof providing a shoulder 452 adjacent to the upper end of the device 300 as viewed in FIG. 11, the cylindrical sleeve 450 having an inner surface 453 disposed tightly about the outer surface 303 of the device 300 throughout the facing areas thereof and preferably secured thereto and in good thermal connection therewith. There also is provided an outer annular outer surface 454 on the portion of the sleeve 450 disposed between the shoulder 452 and the upper outer end thereof. The cylindrical sleeve 455 has a reduced portion 456 on the inner end thereof providing a shoulder 457 adjacent to the lower end of the device 300 as viewed in FIG. 11, the cylindrical sleeve 455 having an inner surface 458 disposed tightly about the outer surface 303 of the device 300 throughout the facing areas thereof and preferably secured thereto and in good thermal connection therewith. There also is provided an annular outer surface 459 on the portion of the sleeve 455 disposed between the shoulder 457 and the lower outer end thereof. Finally it is pointed out that the inner ends of the cylindrical sleeves 450 and 455 abut against each other at substantially the longitudinal midplane of the device 300 and are symmetrically disposed about the midplane of the device 300 in a longitudinal direction.

In order to provide the necessary crossed-field, i.e., a magnetic field, within the device 300, a single magnet coil 460 has been provided to generate the magnetic field through the various spaces within the device 300. The magnet coil 460 is shaped as a torus, is wound of electrically conductive wire, and as illustrated, is disposed with the longitudinal midplane thereof at the longitudinal midpoint or midplane of the device 300. The upper and lower surfaces of the magnet coil 460 are spaced inwardly away from the outer ends of the device 300, and as is more clearly illustrated in FIG. 12, are spaced inwardly with respect to the anges 374 on the pole pieces 370. Further, the magnet coil 460 is arranged so that the magnetic field produced thereby has the longitudinal axis thereof coincident with the longitudinal axis of the device 300 so as to provide a maximum uniformity and strength of the magnetic field in the device 300.

There further has been provided a magnet yoke 461 enclosing the magnet coil 460 and coupling the magnetic field therefrom to the pole pieces 370. The magnet yoke 461 more particularly includes an annular top plate 462 that has a central opening therein receiving the sleeve 450 therethrough, an annular bottom plate 464 that has a central opening therein receiving the sleeve 455 therethrough, the top plate 462 having an annular upstanding ange 463 integral therewith and surrounding the.sleeve 455 and disposed opposite the ange 374 on the top pole piece 370 (see FIG. 12), and the bottom plate 464 having an annular depending flange 465 integral therewith and surrounding the sleeve 455 and disposed opposite the ange 374 on the bottom pole piece 370. The outer edgeS of the top plate 462 and the bottom plate 464 are joined by an annular plate 466. It will be understood that the magnet yoke 461 including the top plate 462 and the bottom plate 464 and the annular plate 466 is formed of a metal having a high magnetic permeability, such for eX- ample as low carbon steel or soft iron, whereby to provide a path of exceedingly low reluctance for magnetic ux. Although the flanges 463 and 465 are spaced a short distance from the adjacent anges 374 of the associated pole pieces 370, with the non-magnetic copper layers 302 and 450 or 455, as the case may be, disposed therebetween, the spacing is so close as to provide in fact a good magnetic path, whereby the magnetic flux generated by the magnet coil 460 is well coupled to the pole pieces 370 and thus distributed through the interaction space of the device 300 thereby, It will be understood that the conductor 60 is connected to one terminal of the magnet coil 46,0, the other terminal of the magnet coil 460 being connected by a conductor 468 to a cooling fin 470, the conductor 468 being connected thereto as at 469. As a consequence, when operating potentials are applied to the conductor 60 the coil 460 generates a strong magnetic flux which is directed into and distributed through the interaction space of the device 300 by means of the magnet yoke 461 and the pole pieces 370.

In order to provide the required cooling for the device 300, the sleeves 450 and 455 carry thereon stacked arrays of cooling fins 470, each of the cooling fins 470 having an annular flange 471 thereon encircling the adjacent sleeve 450 or 455, as the case may be, and suitably secured thereto as by brazing, thus to provide a good thermal contact therebetween.

From the above it will be seen that there have been provided an improved crossed-field discharge device, an improved microwave oscillator circuit incorporating the crossed-field discharge device therein,4and an improved output coupler and filter structure for the crossed-field discharge device which fulfill all of the objects and advantages set forth above. More particularly, there has been provided an improved crossedfield discharge device for use at microwave frequencies which is of simple and economical construction and arrangement, the device being particularly adapted for operation with loW applied potentials between the anode and the cathode thereof. The improved crossed-field discharge device provides a high output of microwave energy in proportion to the physical dimensions thereof, whereby to permit the [miniaturization of microwave circuits employing the improved crossedfield discharge device of the present invention.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A crossed-field discharge device comprising an anode structure defining an axially extending space therethrough, a pair of pole pieces respectively arranged adjacent to the opposite ends of said anode structure, a plurality of axially extending anode segments on said anode structure and projecting radially into said axially extending space and providing a corresponding plurality of axially extending anode recesses therebetween, a plurality of rods respectively disposed in said anode recesses and respectively spaced from the ones of said anode segments adjacent to said anode recesses, means electrically interconnecting said rods at corresponding ends thereof, an axially extending annular ,emissive cathode disposed in said axially extending space and cooperating with said anode structure to define an axially extending annular interaction space,

a heater for said cathode disposed therein, a rst connector commonly electrically connected both to said cathode and to one terminal of said heater and extending outwardly from said device through one end of said anode structure, a second connector connected to the other terminal of said heater and extending outwardly from said device through said one end of said anode structure, means enclosing and sealing the other end of said anode structure and the associated end of said axially extending space, and an end structure enclosing and sealing said one end of said anode structure and the associated end of said axially extending space and receiving said connectors therethrough for mechanically supporting said cathode and said heater with respect to said anode structure while providing electrical insulation among said anode structure and said connectors.

2. The crossed-field discharge device set forth in claim 1, wherein said end structure is the only electrically insulating seal for said device.

3. The crossed-field discharge device set forth in claim 1, wherein said rst connector is connected to the end of said cathode toward said one end of said anode structure, the end of said cathode disposed away from one end of said anode structure is connected to the terminal of said heater disposed away from said one end of said anode structure, and said second conne-ctor is connected to the terminal of said heater disposed toward said one end of said anode structure.

4. The crossed-held discharge device set forth in claim 1, wherein said cathode includes an annular Wall of electrically conductive 4material completely enclosing said heater and extending to the exterior of said device through said one end of said anode structure, thereby to prevent the introduction of RF energy into said heater.

5. A crossed-field discharge device comprising an anode structure dening an axially extending space therethrough, a pair of pole pieces respectively arranged adjacent to the opposite ends of said anode structure, a plurality of axially extending anode segments on said anode structure and projecting radially into said axially extending space and providing a corresponding plurality of axially extending anode recesses therebetween, a plurality of rods respectively disposed in said anode recesses and respectively spaced from the ones of said anode segments adjacent to said anode recesses, means electrically interconnecting said rods at corresponding ends thereof, an axially extending annular emissive cathode disposed in said axially extending space and cooperating with said anode structure to define an axially extending annular interaction space therebetween, a heater for said cathode disposed therein, an annular outer conductor commonly electrically connected both to said cathode and to one terminal of said heater and extending from said device through one end of said anode structure, an inner conductor disposed Within said outer conductor and electrically connected to the other terminal of said heater and extending outwardly from said `device through said one end of said anode structure, means enclosing and sealing the other end of said anode structure and the associated end of said axially extending space, and an end structure enclosing and sealing said one end of said anode structure and the associated end of said axially extending space for mehanically supporting said cathode and said heater with respect to said anode structure while providing electrical insulation among said anode structure and said conductors.

6. The crossed-field discharge device set forth in claim 5, wherein said end structure includes a first mechanically supporting and electrically insulating seal between said outer conductor and said one end of said anode structure, and a second mechanically supporting and electrically insulating seal between said outer conductor and said inner conductor.

7. The crossed-field discharge device set forth in claim 5, wherein said cathode includes an annular wall of electrically conductive material completely enclosing said heater and extending to the exterior of said device through said one end of said anode structure, thereby to prevent the introduction of RF energy into said heater.

8. A crossed-held discharge device comprising, an annular anode structure defining therein an outer annular axially extending space enclosed thereby and an inner axially extending space extending therethrough and a radially extending passage interconnecting said outer axially extending space and said inner axially extending space at the longitudinal midsection of said anode structure, said radially extending passage dividing said anode structure into a first anode section disposed adjacent to one end thereof and a second anode section disposed adjacent to the other end thereof, a plurality of axially extending anode segments on the inner surfaces of said anode sections and projecting radially into said inner axially extending space and providing a corresponding plurality of axially extending anode recesses therebetween, a plurality of axially extending rst rods on said first anode section respectively disposed in the anode recesses in said second anode section and respectively spaced from the adjacent ones of said anode segments in said second anode section, a plurality of axially extending second rods on said second anode section respectively disposed in the anode recesses in said rst anode section and respectively spaced from adjacent ones of said anode segments in said first anode section, an axially extending annular emissive cathode disposed in said axially extending space and cooperating with said anode structure to define an axially extending annular interaction space, means for establishing a unidirectional magnetic field extending axially through said outer axially extending space and said interaction space, a heater for said cathode disposed therein, a first connector commonly electrically connected both to said cathode and to one terminal of said heater and extending outwardly from said device through one end of said anode structure, a second connector connected to the other terminal of said heater and extending outwardly from said device through said one end of said anode structure, means enclosing and sealing the other end of said anode structure and the associated end of said axially extending space, and an end structure enclosing and sealing said one end of said anode structure and the associated end of said axially extending space and receiving said connectors therethrough for mechanically Supporting said cathode and said heater with respect to said anode structure while providing electrical insulation among said Vanode structure and said connectors.

9. The crossed-held discharge device set forth in claim 8, wherein the portions of said anode structure defining said outer axially extending space cooperate to provide a portion of an outer coaxial transmission line for accommodating an axially extending RF wave therein, the anode segments on said first anode section and said second rods cooperate to provide a first portion of an inner coaxial transmission line for accommodating an axially extending RF wave therein, the anode segments on said second anode section and said first ro-ds cooperate to provide a second pogtion of an inner coaxial transmission line for accommodating an axially extending RF wave therein, and said radially extending passage interconnects said outer coaxial transmission line and the first and second portions of said inner coaxial transmission line to provide a folded resonant cavity having an operating frequency equivalent to twice the combined length of said coaxial transmission lines.

10. The crossed-field discharge device set forth in claim 9, wherein said outer coaxial transmission line has the ends thereof closed, and said inner coaxial transmission line has the outer ends thereof open.

11. The crossed-field discharge device set forth in claim 8, wherein the radial distance between the outer surface of said cathode structure and the outermost portion of the adjacent one of said anode recesses is less than that required to accommodate a radial standing wave at the operating frequency of the folded resonant cavity for said device, and the radial distance between the outer surface of said cathode structure and the outermost portion of said outer axially extending space is less than that required to accommodate a radial standing wave at an operating frequency of the folded resonant cavity for said device.

12. The crossed-field discharge device set forth in claim 8 wherein said anode structure is symmetrical about a plane normal to the axis of said anode structure midway between the ends thereof.

13. A microwave oscillator comprising a crossed-field discharge device including an anode structure defining an axially extending space therethrough, a plurality of axially extending anode segments on said anode structure and projecting radially into said axially extending space and providing a corresponding plurality of axially extending anode recesses therebetween, a plurality of rods respectively disposed in said anode recesses and respectively spaced from the ones of said anode segments adjacent to said anode recesses, mean electrically interconnecting said rods at corresponding ends thereof, an axially extending annular ernissive cathode disposed in said axially extending space and cooperating with said anode structure to define an axially extending annular interaction space, a heater for said cathode disposed therein, a first connector commonly electrically connected both to said cathode and to one terminal of said heater and extending outwardly from said device through one end of said anode structure, a second connector connected to the other terminal of said heater and extending outwardly from said device through said one end of said anode structure, means enclosing and sealing the other end of said anode structure and the associated end of said axially extending space, and an end structure enclosing and sealing said one end of said anode structure and the associated end of said axially extending space and receiving said connectors therethrough for mechanically supporting said cathode and said heater with respect to said anode structure while providing electrical insulation among said anode structure and said connectors, said anode structure defining a frequency determining resonant cavity for said device; means for producing a unidirectional magnetic field extending axially through said axially extending space; and means for producing a unidirectional electrical field between said anode structure and said cathode.

14. The microwave oscillator set forth in clairn 13, and further comprising an output connection coupled to said anode structure, said unidirectional magnetic field and said unidirectional electrical field and said resonant cavity cooperating to establish an axially extending RF wave in said axially extending space and having associated therewith RF electrical fields and RF magnetic fields normal to the axis of said device and extending into said interaction space, said first connector and said anode connection cooperating to remove RF energy from said axially extending space utilizing said cathode structure as a probe interacting with said RF fields.

15. A microwave assembly comprising a crossed-field discharge device including an anode structure defining an inner axially extending space therethrough, a pair of pole pieces respectively arranged adjacent to the opposite ends of said anode structure, an axially extending annular ernissive cathode disposed in said axially extending space and cooperating with said anode structure to define an axially extending annular interaction space therebetween, a heater for said cathode disposed therein, a first connector commonly electrically connected both to said cathode and to one terminal of said heater and extending outwardly from said device through one end of said anode structure, a second connector connected to the other terminal of said heater and extending outwardly from said device through said one end of said anode structure, means enclosing and sealing the other end of said anode struc- 24 ture and the associated end of said axially extending space, and an end structure enclosing and sealing said one end of said anode structure and the associated end of said axially extending space and receiving said connectors therethrough for mechanically supporting said cathode and said heater with respect to said anode structure while providing electrical insulation among said anode structure and said connectors; an anode connection at said one end of said anode structure extending outwardly therefrom, said anode connection and said first connector cooperating to provide output connections for said device for removing RF energy therefrom; and a microwave coupling structure including a pair of RF input terminals connected respectively to said anode connection and said first connector, a pair of DC input terminals for connection to a source of DC potential, a pair of AC input terminals for connection to a source of low voltage AC potential, a pair of output terminals for connection to a load for RF energy, means providing a DC connection between one of said DC input terminals and said anode connection via one of said RF input terminals, and RF rejection filter interconnecting the other of said DC input terminals and one of said AC input terminals and said first connector via the other of said RF input terminals and providing a DC connection therebetween, means interconnecting the other of said AC input terminals and said second connector and providing a DC connection therebetween, and means capacitively coupling said RF input terminals respectively to said RF output terminals.

16. The microwave assembly set forth in claim 15, and further comprising, means for establishing an axially extending RF wave in said axially extending space and having associated therewith RF electrical elds and RF magnetic fields normal to the axis of said device and extending into said interaction space, said anode connection and said first connector cooperating to provide output connections for said device for removing RF energy from said axially extending space utilizing said cathode as a probe interacting with said RF fields. v

17. The microwave assembly set forth in claim 15, and further comprising, an RF filter disposed between said RF input terminals and said RF output terminals and serving to filter the second and higher harmonics of the operating frequency of said device from said RF output terminals.

1S. The microwave assembly set forth in claim 15, and further comprising structure shielding the heater and said second connector from RF energy and to prevent the introduction of the RF energy into the associated low voltage AC source via said means interconnecting the other of said AC input terminals and said second connector.

19. A microwave assembly comprising a crossed-field discharge device including an anode structure defining an inner axially extending space therethrough, a pair of pole pieces respectively arranged adjacent to the opposite ends of said anode structure, an axially extending annular ernissive cathode disposed in said axially extending space and cooperating with said anode structure to define an axially extending annular interaction space therebetween, a heater for said cathode disposed therein, an annular cathode connector commonly electrically connected both to said cathode and to one terminal of said heater and extending from said device through one end of said anode structure, an inner heater connector disposed within said cathode connector and electrically connected to the other terminal of said heater and extending outwardly from said device through said one end of said anode structure, means enclosing and sealing said one end of said anode structure and the associated end of said axially extending space for mechanically supporting said cathode and said heater with respect to said anode structure |while providing electrical insulation among said anode structure and said connectors; an annular anode connector to said one end of said anode structure and surrounding said cathode connector and cooperating therewith to provide output connections for said device for removing LRF energy from said axially extending space; and a microwave coupling structure including a first annular outer conductor connected to said anode connector, a first annular inner conductor disposed within said first annular outer conductor and connected to said cathode connector, said first outer conductor and said first inner conductor providing RF input terminals so said coupling structure, a second annular outer conductor extending from and angularly disposed with `respect to said first outer conductor, a second inner conductor connected to said first inner conductor and extending into said second outer conductor, first and second DC input terminals for said coupling structure, means interconnecting said first outer conductor and said first DC input terminal to provide a DC connection therebetween and to said anode connector, an RF rejection filter interconnecting the outer ends of said first inner conductor and said first outer conductor and said second DC input terminal to provide a DC connection therebetween and to said anode connector while preventing RF coupling therebetween, a third annular outer conductor concentrically arranged with respect to said second outer conductor and electrically insulated therefrom and capacitively coupled thereto, and an annular inner conductor having said second inner conductor extending thereinto and electrically insulated therefrom and capacitively coupled thereto, said third outer conductor and said annular inner conductor providing RF output terminals respectively coupled to said anode connector and cathode connector for removing RF energy from said axially extending space.

20. The microwave assembly set forth in claim 19, wherein said cathode includes an annular wall of electrically conductive material completely enclosing said heater and extending to the exterior of said device and connected to said annular cathode connector, thereby to prevent the introduction of RF energy into said low voltage AC source via said heater and said heater connector.

21. The microwave assembly set forth in claim 19, wherein said RF rejection filter includes the outermost portion of said first annular outer conductor and an annular filter conductor telescopically associated therewith and having electrical insulation therebetween, the outer end of said annular filter conductor being closed and electrically connected to the outer end of said first inner annular conductor, said first outer annular conductor and said filter conductor overlapping a distance equivalent to 1A wavelength of the RF energy in said device.

22. The microwave assembly set forth in claim 19, and further comprising means for establishing an axially extending RF wave in said axially extending space and having associated therewith RF electrical fields and RF magnetic fields normal to the axis of said device and extending into said interaction space, said anode connector and said cathode connector cooperating to provide output connections for said device for removing energy from said axially extending space using said cathode as a probe interacting with said RF fields.

23. The microwave assembly set forth in claim 19, wherein said third outer conductor telescopically overlaps said second outer conductor a distance equivalent to 1A wavelength of the operating frequency of said device and said annular inner conductor telescopically overlaps said second inner conductor a distance equivalent to 1A wavelength of the operating frequency of said device, whereby to provide an RF filter for the second and higher harmonics of the operating frequency of said device to prevent introduction thereof into said R-F output terminals.

24. A microwave coupling structure for coupling potentials to a crossed-field discharge device having a heater connection disposed within an annular cathode connection that is in turn disposed within an annular anode connection, said coupling structure comprising a pair of annular RF input terminals for telescoping connection respectively to said cathode connection and said anode connection, a pair of DC input terminals for connection to a source of DC potential, a pair of AC input terminals for connection to a source of low voltage AC potential, a pair of output terminals for connection to a load for RF energy, means providing a DC connection between one of said DC input terminals and said RF input terminal connected to said anode connection, an RF rejection filter interconnecting the other of said DC input terminals and said RF input terminal connected to said cathode connection and providing a DC connection therebetween, means interconnecting one of said AC input terminals and said other DC input terminal, means interconnecting the other of said AC input terminals and said heater connection, and means capacitively coupling said RF input terminals respectively to said RF output terminals.

25. A microwave coupling structure for coupling potentials to a crossed-field discharge device having a heater connection disposed within an annular cathode connection that is in turn disposed within an annular anode connection, said coupling structure comprising a first annular outer conductor for connecting to the annular anode connection, a first annular inner conductor disposed within said first outer conductor for connecting to the annular cathode connection, said first outer conductor and said first inner conductor providing RF input terminals for said coupling structure, a second annular outer conductor extending from and angularly disposed with respect to said first outer conductor, a second inner conductor connected to said first inner conductor and extending into said second outer conductor, first and second DC input terminals for said coupling structure for connection to a source of DC potential, first and second AC input terminals for connection to a source of low voltage A-C potential, means interconnecting said first outer conductor end said first DC input terminal to provide a DC connection therebetween, an RF rejection filter interconnecting s aid first inner conductor and said second DC input terminal to provide a DC connection therebetween while preventing RF coupling therebetween, means connecting said first AC input terminal to said second DC input terminal, means connecting said second AC input terminal to said heater connection, a third annular outer conductor concentrically arranged with respect to said second outer conductor and electrically insulated therefrom and capacitively coupled thereto, and a third annular inner conductor having said second inner conductor extendino theremto and electrically insulated therefrom and capaci:- tively coupled thereto, said third outer conductor and said third inner conductor providing RF output terminals for said coupling circuit.

26. A microwave coupling structure set forth in claim 25, wherein the axes of said output terminals are disposed substantially normal to each other.

27. The microwave coupling structure set forth in claim 25, wherein said RF rejection filter comprises an annular RF choke disposed in the outer end of said first outer conductor and telescopically associated therewith and electrically insulated therefrom, the outer end of said RF choke being closed and connected to said first inner conductor and having a DC connection with said second DC input terminal and said first AC input terminal.

28. The microwave coupling structure set forth in claim 27, wherein the outer end of said first outer conductor and said annular RF choke overlap a distance equivalent to Mi the wavelength of the RF energy in the associated crossed-field discharge device.

29. The microwave coupling structure set forth in claim 25, wherein said third outer conductor and said second outer conductor telescopically overlap a distance equivalent to 1A wavelength of the operating frequency of the associated crossed-field discharge device, and said second inner conductor and said third annular inner conductor overlap a distance equivalent to 1A wavelength of 

